Hydraulic machines of the piston-operated type



HYDRAULIC MACHINES OF THE msmomorrsmmn TYPE Filed Feb. 12, 1963 June1955 w. P. BILLINGTON ETAL 3 Sheets-Sheet 1 FIG. 4.

INvENToRS WILLIAM P. BILLINGTON DAVB F. HowaoN ATTORNEY J1me 1965 w. P.BILLINGTON ETAL 3,190,224

HYDRAULIC MACHINES OF THE PISTON-OPERATED TYPE Filed Feb.'12, 1963 3Sheets-Sheet 2' 9 MN QM. VN oN MN QN mfi/ w w Q flwwlm -f x a a 3 O MW 3o Wm M a a 3% 2 AW INVEN TOR 5 WILLIAM F. BILLINGTON DAwb F. HowsoNATTORNEY June 965 w. PQBILLINGTON ETAL 3,190,224

HYDRAULIC MACHINES OF THE PISTON-OPERATED TYPE Filed Feb. 12, 1963 sSheets-Sheet 5 '57 52 43 saif 3s 49 J9 o- 2' /5 53' :2 F16. 3. 4a- 45 4827 I7 29 J3 J7 INVEN'TQRS WILLIAM PBILUNGTON DAVID F. Henson UnitedStates PatentfO 3,196,224 HYDRAULIC MACHINES OF THE PISTON- OPERATEDTYPE 7 William Peter Billington, Flitwiclr, and David Frank Howson,Brickhill, England, assignors to National Research DevelopmentCorporation, London, England, a British corporation Filed Feb. 12, 1963,Ser. No. 257,997 Claims priority, application Great Britain, Feb. 15,1962,

5,862/62 6 Claims. (Cl. 103-37) V This invention relates to hydraulicmachines of the piston type, for example swashplate oreccentric-operated piston-type rotary motors or pumps, each cylinder ofwhich is provided with an auxiliary piston arranged either to slidewith'the main piston in the cylinder or to be locked against slidingmovement in the cylinder, for the purpose of altering the swept volumeof the machine to vary the speed or the delivery of the machine as thecase may be. Thus for example in the case of a hydraulic motor, forlow-speed high-torque operation the auxiliary piston slides with themain piston in the cylinder, but it remains fixed in the cylinder andthereby decreases the swept volume of the motor for high-speed operationwith lowertorque at the same input of hydraulic fluid.

According to the present invention, in a hydraulic pump or motor of thetype specified the means provided for selecting the auxiliary piston toremain stationary in the cylinder or to move with the main pistoncomprises hydraulic locking means associated with the auxiliary piston,the locking action of which means is performed not by a solid lockingbolt but by the resultant thrust produced by incompressible. pressurisedhydraulic fluid acting on one or more surfaces of the auxiliary piston.

The operation of the hydraulic locking means, may be controlled bymechanical means if desired, but in a preferred arrangement it isarranged to take place automatically in response to a variation ofhydraulic pressure .in a hydraulic system connected to the machine.

For example, where themachine is incorporated in a hydraulictransmission system maintained at an elevated base pressure to reducecavitation, the locking or release of the auxiliary piston by ehydraulic locking means may be selected in response to a change in thebase pressure, sometimes referred to as the boost pressure.

. Hitherto, in such machines the. control of the auxiliary piston hasbeen efiected by mechanical means by which the auxiliary piston iseither positively locked by means of a mechanical latch or bolt to themain piston to slide therewith in the cylinder, or is similarly lockedmechanically in the cylinder against movement with the main piston. Suchmechanical controlmeans however is subject to variousgdisadvantages,including'the considerable mechanical shock introduced by the operationof the locking means.

In one arrangement of the present invention the auxiliary pistoncomprises a movable hydraulic valve shuttle member arranged to move inresponse to variatiouin the base pressure in the applied. hydraulicisystem between a position in whichitadmits the full working pressure ofthe system to one side of the auxiliary piston but shuts 1 ed the systempressure from the other side thereof, thereby hydraulicallylocking theauxiliary piston in an extreme position against movement in thecylinder, and a second position in which the system pressure is admittedin balance to both sides of the auxiliary piston to permit it to movewith the main piston.: e

the bore of the sleeve. An alternative arrangement has been devisedhowever, in which the sleeve comprises the main piston and is coupled tothe input or output member of the machine, as the case may be, whilstthe auxiliary piston comprises a free piston which slides in the bore ofthe sleeve. 7

The invention may be carried into practice in various ways, but twospecific embodiments will now be described by way of example only withreference to the accompanying drawings, in which FIGURE 1 is a generalview of a hydraulic motor, FIGURE 2 is a fragmentary sectional view ofone cylinder of the motor of FIGURE 1 with the auxiliary piston sleevehydraulically lockedgto the main cylinder, 7

FIGURE 3 is a view similar to FIGURE 2 but showing the auxiliary pistonsleeve free to slide with the main piston, and

, FIGURE 4 is a view similar to FIGURE 2 of one cylinder of a modifiedembodiment of motor.

In the embodiment of FIGURES 1 to 3, a hydraulic motor generally.indicated at 10 comprises an annular housing 11 in which are formed anumber of radiallyextending cylinders 12 each provided withitsassociated detachable cylinder head 13 secured by means of boltsorstudsld to the top of the associated projectingcylinder block 15. Asseen in FIGURES l and 2 the annular housing 11'is formed with anexternal circumferential channel 16 in which the cylinder heads 13 andprojecting cylinder blocks 15 lie. r t

The motor 10 has a corresponding number of pistons 17 each slidableradially in one of the cylinders 12 in the housing 11. The pistons 17operate an eccentric 18 which is mounted on the main output shaft 19 ofthe motor in a central cylindrical recess 20 within the housing 11. Thecylindrical eccentric 18 is mounted with its axis 21 radially displacedfrom the axis 22 of the output shaft. Each piston 17 is formed at itsradially inner end with a part spherical bearing foot 23 which sits inacor- .respondingly formed bearing recess of a rocker: shoe 24, the,radially inner surface of each rocker shoe 24 being of part-cylindricalform and being in contact with abearing ring 25 coaxially journalled onthe eccentric 18, so that reciprocating movement of the pistons 17 inthe radial direction producesrotation of the eccentric 18 and ,ofthe"output shaft 19 about the axis 22 of the latter. The

rocker bearings, 23, 24 are lubricated by pressure fluid supplied fromthe interior of the cylinder via passages 26 formedin the piston '17. V

As shown in FIGURES. 2 and 3, each piston 17 is surrounded by acylindrical sleeve 27, in the bore 28 of which sleeve the piston 17 is aclose sliding fit. Each sleeve 27 ,is itself a close sliding lit in theassociated cylinder 12 and thus constitutes an auxiliary piston. Eachsleeve 27 has an iu-turned flange 29 at its radially outer end which.ex-

tends over the crown of ,the main piston=17 and acts as a stop, to limitrelative sliding movement in one direction. The cylinder block 15 ofeach cylinder 12 is formed 'with a main inletpassage 30 which isconnected to a source of hydraulic fluid under pressure via suitableporting or valvingtnot shown), ofconventional design. The assoe oiatedcylinder head 13 is also forme'dwith a miain'inlet passage 31 alignedwith the. passage 30, through which passage 31 hydraulic fluid underpressure is admitted to the interior of the cylinder 12 above the piston17 through an extension tube 32 which projects radially inwardly into arecess 33 formed in the' crown of the piston '17. A movable valve sleeve35'surrounds the extension tube 32 and is spring-lbiassed in a radiallyoutward directionby a valve spring 36 acting between an external flange37 on the inner end of'the tube 3 2 and an internal flange 38 formed inthe ,bore of the valve sleeve, 35. The cylindricalbody 3-9 of the valvesleeve across the cylinder 12 at its upper end, and the outer part ofthe valve sleeve 35 outside the cover plate 40 is formed as a piston 41which is a close sliding fit in the cylindrical bore 42 formed in thecylinder head 13. Thus the valve 35 is a close sliding fit in 'anaperture formed in a cover plate 40 which extends sleeve 35 is movablein thecylinder head in radially 'ina ward and outward directionscoaxially with the main piston '17. Sealing rings 43,44 and 45 areprovidedto seal the valve sleeve 35 in sliding contact with the surfacesof the cylinder head bore .42, the aperture in the cover" plate 40 andthe flange 29 of the auxiliary piston sleeve '27. 1

An auxiliary passage 48 formed ineach cylinder block 15 is connected toa point of a hydraulic system associated with .the motor at the systembase or boost pressure. The passage 48 is inalignment witha'corresponding auxwill thus close the open inner. edge, of the narrowannular V clearance 52 between the pistonsleeve 27 and the'cover plate40, sealing off this clearance space from the working 7 pressure appliedto the crown of the main piston 17. However the working pressure willstill acton the radially inner face of the flange 29 of the pistonsleeve 27, so that the sleeve 27 will be subject to anoutwardly-directed hydraulic thrust which will keep it hydraulicallyclamped against thecoverplate 40.; 'Now the piston sleeve 27 will beretained locked in the main cylinder 1 2 by this hydrau-lic clampingforce, and the main piston 17 willieciprocate alone within the bore 28of the piston sleeve 27,

sliding relatively to the'lockedpiston sleeve 27 which surili-arypassage'49 formed 'in the cylinder head 'l3 and leading into the bore42, so. that this'steady hydraulic base pressure is applied to theinterior of the cylinder head bore 42 beyond the piston 41 of the valvesleeve 35. The

strength of the valve spring 36 is so chosen in relation to the basepressure and to the efleot-ive areaof the piston 41 ,7

on the valve sleeve 35 that whenthe base pressure is at a'predeterminedhigh value, say 100 p.s.i.,'the resultant hy-.

draulic thrust on the piston 41 of the valve sleeve35 over-' comes theforce of the spring 36-and moves the valve sleeve 35 radially inwardlyto its innermost position as illustrated in FIGUREZ. In this positiontheinner face of the piston 41 engagesagainst the outer face of the coverhead bore 42 is reduced to a predetermined low value, say

50 p.s.i. the valve spring 36 prevails and moves the valve sleeve 35radially outwardly to the position shown in FIGURES. 7

The radially outer end of the sleeve 27 constituting cumferential flange51 which abuts against the inner face of the cover plate 40 to limit theoutward movementof the, auxiliary piston sleeve 27. In the outermostposition of the piston sleeve 27 as illustrated in 2 and 3, a narrowannular clearance 52 is defined between the inner face of the coverplate 40 and the outer end face of the s auxiliary piston is formed withan axially projecting cirplate to limit the radially inward movement ofthe valve sleeve 35. -However when the hydraulic base'pres-sure suppliedthrough the passage-s48 and 49 to the cylinder position of the valvesleeve 35 the annular clearance 52 is thus subjected to the hydraulicworking pressure prevailing in the cylinder head inlet passage 31 and,via the bore of the extension tube 32, in the recess 33in the crown'ofthe piston 17, which working pressure acts on the piston 17.Since'the-annular area thus exposed at the radially outer end of theauxiliary piston sleeve 27 is greater than -the oppositely facingannular meant the inner side of the flange 29 of the sleeve 27, thesleeve" 27 will thus be sub-- ject to a resultanthydraulic thrust in theradially inward,

' directionand will thus move radially inwardly together with the mainpiston 17 sliding in the main cylinder 12 1 7 under the thrust'of theworking pressure, so that the two pistons together apply a drivingtorque to the'outpu't'shaft 19 via the eccentric 18. g

However when the base pressure in the system is.

changed to as higher va-lue of 100 p.-s.i. and moves the -valve sleeve35 to its radially inner position as illustrated in FIGURE 2, thenasthepiston sleeve' 27 is returned to its outer position by the next outwardstroke of the main piston 17, the cylindrical body 39 of thevalve sleeve35 will slide into the cylindrical aperturedefined by the in-; turnedflange 2.9 at the top of the piston sleeve 27 and roundsit.

To prevent hydraulicfluid being trapped between-the cover plate 40 andthe outerv end face of the piston sleeve 27 as the latter approaches itsextreme outer position, a

bypass passage 53 is formed in the flange 29 of the piston:

sleeve 27 and incorporates a nonreturn valve 54 of the ball type. Anytrapped fluid can thus escape'fromthe annular clearance 52 through thebypass passage, but the iballvalve prevents the flow of'fiuid throughthe bypass passage 53 in the opposite direction into the clearance 52.1"A bleed passage 57 extends through the wall ofthe cylinder head 13 toprevent fluid becoming trapped beneath the piston 41, and a second bleedpassage 58 provided with anon-return valve 59 extends from the bore .42of the cylinder head back into the inletpassageB l. Theauie iliarypassage 48 in the cylinder block 15 is provided with its own non-returnvalve 50.

Thus by the simple operation of changing the system 1 'base pressurefrom one value to the other, which can be done by a simple two-positionhydraulic slide valve,zthe movable valve sleeve in each cylinder head'13 canwbe caused to move from' its outer position of FIGURE 3 to itsinner position of .FIGURE. 2, or vice versa, there- 'by causing theauxiliary piston sleeve '27 either to remain stationary in a lockedposition in the cylinder 12 whilst the main piston 17 reciprocates alonein the cylindenfor high speed; operation of the motor, or to slide withthe main piston 17 in the cylinder 12 for low speed operation withgreater output torque.

In the modified embodiment illustrated in FIGURE 4, in which similarparts are given the same. reference num-i ber's, each-cylinder 12 isprovided with a main piston which is in the formof a'cylindrical sleeve60 which'is slidable within the cylinder 12, the piston sleeve'60 beingformed with a bearing foot 61 at its inner end whichacts on the bearingring 25 of the eccentric 18 via a rocker shoe 24', whilst the auxiliarypiston in this case c0m-, prises a solid cylindrical piston 62 which isslidable-inthe bore 63 of the main piston sleeve 60. The auxiliarypiston 62 is formed at its outer end with an" external"radially-protruding circumferential flange 64 which overlies theannular end face 65. of the piston sleeve 60 and limits relative slidingmovement between the sleeve 60 and the auxiliary piston 62 in onedirection. The mov-' able valve member in this case comprises a valvecollar 66 "slidably mounted on a fixed mushroom-shaped stud- 67 fo rmedintegrally with the cylinder head 13 and protruding'inw'ardly withinitsjbore 42, the valve collar 66.

being spring-biassed in the radially outward direction by means of. ahelical compression. spring 68... The valve collar 66 is formed-with adepending skirt 70, and when. theicollar 66 is moved to its radiallyinnermost position. as illustrated in'FIGURE4 by theaction of thesystemv base pressure when-the'latter is selected to its-highi valuesufiicient to overcome the action of the spring 68, 1 the skirt 70slides over the edge of the flange 64 of the auxiliary piston 62andthereby cuts 01f from ther hydraulic working pressure the clearance 71between the crown ot the auxiliary piston 62 and the ,head lot the stud67, this'clearance 71' being maintained by an axially protruding flange72 formed circumferentially around the outer. edge of the crownof theauxiliary piston :62.

Thus the auxiliary piston 62 will be hydraulically locked to the stud 67with its flange 72 held in abutment against the head of the stud 67 bythehydraulic working of the system acting on the inner annular face ofthe flange 64.

However when the system base pressure, is changed to its predeterminedlower value, so that the valve'collar 65 is raised by its spring 68 tolift the valve skirt 70 clear of the flange 64 and thus to admit theworking pressure of the system to the clearance 71 between the head ofthe stud 67 and the crown of the auxiliary piston 62, the auxiliarypiston 62 'will thereupon be released and will be subject to the systempressure so that it will reciprocate with the main piston sleeve 60 andincrease the swept volume of the motor, thereby producing acorresponding speed reduction and increase in torque of the motor. a

In this embodiment the main working pressure of the hydraulic system isadmitted to the interior of the cylinder .head through a pipe 73, whilstthe system base pressure is admitted into a cylindrical recess 74 formedat the inner end of the interior of the cylinder head 13, through aseparate pressure line 75 leading to an auxiliary passage '76 formed inthe'wall of the cylinder head 13. The valve collar 66 when raised to itsradially-outer position by its spring 68 is a close sliding fitin thecylindrical recess 74, but when the collar 66 is moved inwardly to itsinnermost position as shown in FIGURE 4, it clears the edge of therecess 74 to allow communication between the interior of the recess andthe main bore 42 of the cylinderhead. A non-return valve 77 isprovidedat the entrance to the auxiliary passage 76. Moreover a bleedpassage 78 provided with a non-return valve 79 extends between theauxiliary passage 76 and the main pressure inlet '73 to the head, torelease hydraulic fluid trapped in the recess 74 when the valve collar66 moves to its radially outer position. A bypass passage 80, alsoprovided with a non-return valve 81 extends through the wall of thecylinder head 13 and through the shank of the stud 67 to allow theescape of hydraulic fluid trapped in the clearance 71 between theauxiliary piston 62 and the head of the stud 67, the escaping fluidafter passing through the non-return valve 81 being released into'thebore 42 of the cylinder head outside the valve collar 66.

It will be understood that either of the two embodiments of motordescribed and illustrated may equally Well be employed as a pump, byconnecting the main shaft carrying the eccentric to a suitable drivingmotor. The base pressure used for controlling the valve shuttle member35 or 66 may be derived from the output of the pump using one or moreselectively-controlled restn'ctor valves to provide the requiredpressure variations.

The pressure input passage 30, when the machine is used as a pump, willbecome the pressure delivery or output passage. The same valve mechanism(not shown) which controls the inlet of pressure fluid into the cylinderduring the downward movement of the piston or pistons, and permits fluidto be exhausted from the cylinder during the upward movement of thepiston or pistons, merely needs to be re-timed in order for the machineto operate as a pump. When operating as a pump this valve mechanism willallow discharge of fluid under pressure, when the piston or pistons areascending, and will allow fresh fluid to be drawn into the cylinder froma return line when the piston or pistons are decending.

What we claim as our invention and desire to secure by Letters Patentis: i

1. A hydraulic machine having a cylinder, a cylinder head, a main pistonand an auxiliary piston both movable reciprocally within the cylinder,to vary the volume of the free space within the cylinder between thepistons and the cylinder head, means constraining the auxiliary pistonto a piston stroke of substantially the same length as the overallstroke of the main piston, means for admitting hydraulic fluid to thesaid free space within the cylinder t 6 to'coact simultaneously withboth the-said pistons; and control means for altering the swept volumeof the machine, the said control means having a hydraulic pressure inletfor connection to a source of hydraulic control pressure, and includinga selectively-operable hydraulic shuttle valve connected to the pressureinlet for operation in response to predetermined changes in controlpressure, the

'-'shuttle valve including a sliding shuttle member subject 'to the saidcontrol pressure and movable selectively into a movable selectively intoa second position in which it admits balanced hydraulic pressures toboth sides of the auxiliary piston, whereby the auxiliary piston, isfreed to move in the cylinder together with the main piston.

2. A hydraulic machine as claimed in claim 1 in which the auxiliarypiston is formed with an end face adapted to abut against a cooperatingface of the fixed abutment, and in which the auxiliary piston and theabutment have circumferential edges surrounding their respective saidfaces which edges lie mutually in register with one another inside-by-side relationship when the said faces are in abuttingengagement, and in which the shuttle member when moved into its saidfirst position slides transversely across the said registering edges andseals them against the ingress of hydraulic fluid between the abuttingfaces.

3. A hydraulic machine as claimed in claim 2 in which the auxiliarypiston is a sleeve mounted within and in sliding contact with thecylinder, the sleeve having an internal bore and in which the mainpiston is mounted within and in sliding contact with the bore of thesleeve, and in which the shuttle member is slidable through alignedapertures in the said faces of the abutment and of the auxiliary pistonto seal the adjacent circumferential edges of the said apertures againstthe ingress of hydraulic pressure fluid between said faces.

4. A hydraulic machine as claimed in claim 2 in which the main piston isa sleeve mounted within and in sliding contact with the cylinder andhaving an internal bore, and in which the auxiliary piston is mountedwithin and in sliding contact with the bore of the sleeve, and in whichthe shuttle member has a depending tubular skirt arranged to slide overthe external circumferential surfaces of the auxiliary piston and of thefixed abutment to seal the outer circumferential edges of the saidabutting faces against the ingress of hydraulic pressure fluid betweensaid faces.

. 5. A hydraulic machine having'a cylinder, a cylinder head, a mainpiston and an auxiliary piston both mov-v able reciprocally in thecylinder to vary the volume of the free space within the cylinderbetween the pistons and the cylinder head, means for admitting hydraulicfluid to the'said free space within the cylinder to coact with thepistons, and control means for altering the swept volume of the machine,the said control means including a selectively-operably hydrauliclocking device by which the auxiliary piston is either subjected to anunbalanced hydraulic pressure thrust on one end face thereof by whichpressure thrust the auxiliary piston is held fixedly clamped against afixed abutment in the cylinder, or is freed to move in the cylindertogether with the main piston, the locking device comprising ahydraulically controlled shuttle valve,'having a connection to a sourceof hydraulic control pressure, and including a sliding shuttle membersubject to the said control pressure and movable between a firstposition in which it admits unbalanced hydraulic pressure to one sideonly of the auxiliary piston and shuts off the said hydraulic pressurefrom the other side of the auxiliary piston, and a second position inwhich it admits balanced hydraulic pressures to both sides of theauxiliary piston.

7 r I v a r 6. A hydraulic machine as claimed in glaim'5, in which V 7References Cited by the'Examiner thefauxiliary piston is formed with anend face adapted V t UNI toabut against a eooperating'face of thefixedabutment, STATES PATENTS 7 and in which the auxiliary piston andthe abutment have 10/46 3 '-"'T""'+ 91167 circumferential edgessurrounding their respective said 15' 2182556 5/42 Bowen 91.412 faceswhich edges lie mutually in register with one another 2285476 *6/42Wahlmark 9 1*169 in side-by-sidemelationship when the said faces are ina l abutting engagement, and in whichthe shuttle member t when movedinto its said first position slides transversely FRED ENGELTHALER V i racrosslthe said registeringredges and seals them against' m SAMUELLEVINE, Examiner.

the ingress of hydraulic fluid between the abutting faces. 7

2,716,965- 9/55 Klamp 91168'

1. A HYDRAULIC MACHINE HAVING A CYLINDER, A CYLINDER HEAD, MAIN PISTONAND AN AUXILIARY PISTON BOTH MOVABLE RECIPROCALLY WITHIN THE CYLINDER,TO VARY THE VOLUME OF THE FREE SPACE WITHIN THE CYLINDER BETWEEN THEPISTONS AND THE CYLINDER HEAD, MEANS CONSTRAINING THE AUXILIARY PISTONTO A PISTON STROKE OF SUBSTANTIALLY THE SAME LENGTH AS THE OVERALLSTROKE OF THE MAIN PISTON, MEANS FOR ADMITTING HYDRAULIC FLUID TO THESAID FREE SPACE WITHIN THE CYLINDER TO COACT SIMULTANEOUSLY WITH BOTHTHE SAID PISTONS, AND CONTROL MEANS FOR ALTERING THE SWEPT VOLUME OF THEMACHINE, THE SAID CONTROL MEANS HAVING A HYDRAULIC PRESSURE INLET FORCONNECTION TO A SOURCE OF HYDRAULIC CONTROL PRESSURE, AND INCLUDING ASELECTIVELY-OPERABLE HYDRAULIC SHUTTLE VALVE CONNECTED TO THE PRESSUREINLET FOR OPERATION IN RESPONSE TO PREDETERMINED CHANGES IN CONTROLPRESSURE, THE SHUTTLE VALVE INCLUDING A SLIDING SHUTTLE MEMBER SUBJECTTO THE SAID CONTROL PRESSURE AND MOVABLE SELECTIVELY INTO A FIRSTPOSITION IN WHICH IT ADMITS UNBALANCED HYDRAULIC